Low-dose foliar treatments of the auxin analog 2,4-D reduce potato common scab and powdery scab for multiple potato cultivars and enhance root development

Common scab and powdery scab are major soilborne diseases of potato (Solanum tuberosum). The agricultural cost of both diseases is due to discounting or rejection of infected seed tubers or the formation of lesions on the surface of the tubers that make them unmarketable or, for powdery scab, yield loss. There are no widely accessible and efficacious disease management options for either common scab or powdery scab. In prior work, low-dose foliar treatment with the auxin analog herbicide 2,4-D has been shown to reduce common scab severity of select S. tuberosum cultivars in field and greenhouse settings. In the present study, we address the broad applicability of 2,4-D in disease management by testing the efficacy of 2,4-D treatment across diverse potato cultivars and in suppressing multiple scab diseases of potato. Specifically, we tested whether low-dose 2,4-D treatment is broadly efficacious on multiple white potato cultivars used in Eastern United States potato production. Additionally, we sought to determine whether 2,4-D is efficacious for mitigating powdery scab for Russet Burbank potatoes in a commercial field setting. In two years of field trials, low-dose foliar 2,4-D treatment significantly reduced common scab of all tested potato cultivars with no impact on total tuber yield. In two years of field trials in Tasmania, Australia, low-dose foliar 2,4-D treatment also reduced powdery scab of Russet Burbank potato with no impact on total tuber yield while stimulating potato plant root growth. The ability of 2,4-D to suppress two major tuber diseases and stimulate potato root growth warrants further investigation and optimization for integration into commercial growing systems. •Foliar treatment of 2,4-D suppressed common scab in the field, independent of the potato cultivar.•The distribution of common scab can be highly variable, even in a small field area.•Including spatial trends and soil covariates adjusts for heterogenous disease pressure to better identify treatment effects.•Foliar treatment of 2,4-D also suppressed powdery scab in the field.•2,4-D treatments did not attenuate total tuber yield and actually enhanced potato root growth.